French Pat. No. 1,176,992, published on Apr. 17, 1959, describes a process for the preparation of "solid perfumes", process which consists in the bulky incorporation of a perfume in a synthetic resin. No specific resin however have been mentioned in the cited French patent.
U.S. Pat. No. 3,303,046, granted on Feb. 7, 1967, describes a process for the manufacture of porous compressible plastic materials and suggests the addition to the resulting products of various active ingredients such as pharmaceuticals, deodorants, perfumes or waxes.
Different polyamidic resins have been proposed in the past as gellifying agents. Their use was suggested at small concentrations in large solvent volumes and the resulting dispersions were employed as bases for the preparation of transparent lipsticks or for the manufacture of perfumed candles.
U.S. Pat. No. 3,926,655, granted to HERCULES Inc. on Dec. 16, 1975, discloses a material essentially solvent free consisting of a polyamidic resin containing a perfume oil. By means of the mentioned material, it was possible to manufacture perfumed articles of various forms and good transparency. In general, the polyamidic resins which present the most appropriate features for such a manufacture are those which derive from the condensation of polyamines, especially diamines and triamines, with dibasic acids of relatively high molecular weight, for example the acids derived from the dimerization of diunsaturated carboxylic acids. For instance, the above mentioned U.S. patent describes the condensation product between dimeric linoleic acid and ethylene diamine, which product possesses a molecular weight of between about 6,000 and 9,000. These polymeric products are commercially available under the name of VERSAMID (registered trademark of GENERAL MILLS, Inc.).
U.S. Pat. No. 4,184,099, granted to INTERNATIONAL FLAVORS & FRAGRANCES, Inc. on Jan. 15, 1980, discloses articles destined to deliver volatile substances such as perfumes, insecticides or bactericides. Essentially, these articles consist of polyamidic resins similar to those described in the cited U.S. Pat. No. 3,926,655. However, their molecular weight is higher, having a value of between 9,000 and 12,000. Its properties enable, according to patentees, the incorporation of a higher concentration of the active volatile substance, whose proportion can be as high as 70% of the weight of the resulting perfumed polymeric substrate.
The prior art refers also to processes intended to incorporate different additives, for example dyes or stabilizers, into granulated polymeric materials. This is known as the so-called "master-batch" technique which eminently consists in the preparation of concentrates of the dye or stabilizer into the matrices constituted by the same polymeric material, generally a polyolefin, than that used for the preparation of the end-product. Such a process has become widely accepted within the industry for its simplicity and efficiency [see in this respect: Rubber and Plastics, 42,3283 (1961)].
More recently, there have appeared on the market products with polyolefinic matrices suitable for "master-batch" processes. These are characterized by a high content of perfumed volatile substances. Eminently, they consist of a base of low density polyethylene (LDPE), of polypropylene and of ethylene vinyl acetate [see for example POLYIFF, registered trademark of INT. FLAVORS & FRAGRANCES, Inc.].
These polyolefinic concentrates are generally prepared by incorporating the perfume in suitable mixer at a temperature which varies as a function of the polymeric base. Polyethylene, for example, is treated at a temperature of between about 80.degree. and 180.degree. C. To the thus obtained viscuous mass, the desired perfume is added before cooling and granulation. Such a process presents a major practical drawback inasmuch as the perfume incorporation occurs at high temperature with the consequent loss of a certain amount of volatiles and the modification of the constitution of the composition itself. This process therefore is of limited practical use.
The present invention offers a new solution to the problem set forth by the longlasting homogeneous diffusion of active volatile substances.